<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>在class类外面也可以加字段哦</title>
	</head>
	<body>
		<script>
			class Point {
			    constructor() { }
			}
			let p = new Point();
			p.username = 'zhangsan';
			console.log(p.username);    //zhangsan
		</script>
	</body>
</html>
